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Embryo shipping, cost and success rates

Article

Over the last two decades, embryo transfer has grown in acceptance and is now performed in many horse breeds. The majority of embryo transfers in the United States each year are performed on Arabian and Quarter horses. The American Quarter Horse Association allows multiple foal registrations per year, and the high-dollar Quarter horses are boosting the embryo transfer industry. The embryo transfer technique has not undergone significant innovations for the past few years, but there has been an increasing trend to have embryos shipped to a reproductive facility that manages a large recipient herd. This trend has been supported by encouraging pregnancy rates following embryo transfers from shipped embryos.

Over the last two decades, embryo transfer has grown in acceptance and is now performed in many horse breeds. The majority of embryo transfers in the United States each year are performed on Arabian and Quarter horses. The American Quarter Horse Association allows multiple foal registrations per year, and the high-dollar Quarter horses are boosting the embryo transfer industry. The embryo transfer technique has not undergone significant innovations for the past few years, but there has been an increasing trend to have embryos shipped to a reproductive facility that manages a large recipient herd. This trend has been supported by encouraging pregnancy rates following embryo transfers from shipped embryos.

Choosing a mare

Choosing a recipient mare is critical to any embryo transfer program. The availability of a reliable reproductive facility is helpful in the selection process, considering that most of these facilities have more than 250 mares available each year. The mares used are usually cycling mares; however, ovariectomized and progesterone-treated mares also can be used. The recipient mare must be 100 percent reproductively sound and preferably be young (younger than 10 years old). When using cycling mares, the recipient should ovulate a day prior, the same day or up to three days after the donor mare.

Table 1 Recipient mare fees

Ovulation timing is just the first step in the selection process. The recipient mare must meet some criteria prior to the transfer. The cervical tone and uterine tone determined just prior to the transfer of the embryo is very important to ensure a high pregnancy rate (Carnevale et al, 2000). The presence of a good corpus luteum and the absence of fluid and endometrial folds are additional factors to be evaluated. If the recipient mare fails to meet all of the criteria, she will be omitted for that particular cycle and another mare will be selected for the transfer.

Keeping a small recipient herd on hand to serve a small number of clients can be costly and time consuming — not to mention the stress of not having the right recipient mare when needed.

Table 2 25-day pregnancy rate comparisons

One of the deciding cost factors is that for each donor mare it is necessary to have two or more recipient mares available. Handling the recipient mare herd daily with constant checkups means spending valuable time during the already busy breeding season.

The recipient mares not used that year will require some upkeep until the following year. The mare maintenance can be translated into a few extra dollars if the location is in a cold climate where supplemental feeding becomes necessary throughout the year.

It is not uncommon for clients to believe that any mare, such as an older riding horse, is suitable as a recipient mare. One should never choose a recipient mare based solely on sentimental value. All mares have to be screened in-depth before they are included in a recipient program, to ensure the success of the transfer and to eliminate wasting time. Using a large recipient mare herd from a reproductive facility will provide peace of mind since good recipient mares will always be available. Clients should be instructed in the importance of the recipient mare selection as well as the reasons for the price. As a result, your embryo transfer program can become successful.

Embryo flush and shipment

The embryo flush should be performed between seven to eight days from ovulation, counting the ovulation day as day zero. Day seven or eight embryos seem to be more tolerant to cooling than do smaller embryos (Moussa et al, 2002, Clark et al, 1987).

The embryo is then packed in one of the commercially available transport media (Emcare holding solution or ViGro holding plus) and placed in the Equitainer (Hamilton Thorn, Beverly, MA). In the past, embryos were shipped only in Ham's F-10 which had to be appropriately gassed with a mixture of 5% Co2, 5% O2 and 90% N2 prior to each embryo flush. The Ham's F-10 was usually prepared by the facility carrying the recipient mares and shipped to the veterinarian performing the embryo flush. The unused Ham's F-10 was discarded.

Research has demonstrated that the Emcare embryo holding solution (ICP, Auckland, NZ) and ViGro holding plus (AB Technology, Pullman, WA) have showed the same ability to store and transport equine embryos (Moussa et al, 2003, McCue et al, 2000). Both transport holding media can be stored in the refrigerator during the entire breeding season.

Once in the proper container, the embryo can be shipped overnight or same-day air (counter to counter). According to some studies, and to the high pregnancy rates generally observed, embryos seem to hold well for up to 24 hours in the Equitainer. Even then, the safest and preferred method of shipment among veterinarians is same-day air.

Fee structures

On average, the majority of recipient facilities have similar fee structures. Donor mare owners have the option to lease or to purchase the recipient mare. Leasing is the most-common option. A non-returnable, non-transferable entry fee of $600 to $1,500 is due upon contract signing. This fee will cover the costs for synchronizing a recipient mare for three to four and sometimes unlimited embryo flushes. Additional flushes are subjected to the contract specifics and may require additional fees. The leasing or purchase payment is due upon confirmation of the pregnancy at 16 days, 21 days or after the heartbeat check, depending on the contract. The leasing or purchase fees vary between $2,600 and $4,200. After the recipient mare is confirmed in foal, the donor mare owner will be responsible for paying her boarding fees and any veterinary expenses. In most cases, the donor mare owner can transport the pregnant recipient mare to his or her farm after 35 to 50 days of pregnancy. Some facilities will refund part of the fees in case of an abortion or apply the payment toward another embryo transfer. The recipient mare should be returned to the original facility after weaning the foal, unless there is a purchase agreement. A refund may be applied toward the return of the recipient mare. Failure to return the recipient mare will result in a penalty fee. It is important to read the contract carefully since the rules vary between different facilities.

Pregnancy rates achieved with the transfer of shipped embryos are high and similar to those obtained when the recipient and donor mares are at the same location (Carney et al, 1991, and unpublished data). The quality of the embryo at the time of the collection will affect the pregnancy rates, and they should be taken into consideration when analyzing the success rates for shipped embryos. Check the success rate of the recipient mare facility you choose and the additional details of the contract. Although the costs associated with embryo transfer with shipped embryos may appear high, they can be justified by the good results obtained as recent practice has shown.

Dr. Elizabeth Martinsen received her DVM degree in 1989 from Universidade Federal Fluminense, Rio de Janeiro, Brazil. In 1993, she earned a Masters degree in Equine Reproduction from Texas A&M University. Dr. Martinsen completed a three-year residency program in reproduction at The Ohio State University in 1997 when she also became board certified in theriogenology. During the past eight years, Dr. Martinsen has worked in private practice for Specifically Equine Services, Buellton, Calif., and for Firethorn Equine Services, Lancaster, Ohio. She opened her own practice, Bella Vista Equine Reproductive Services in 2004. Dr. Martinsen is a solo practitioner and offers specialized reproductive services on-farm and in-house.

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